ESM2: rail-clearance-ref — Reference Python implementation for scenario-based GLI/GNI derivation and 2D clearance checkin

This record provides an open reference implementation (Python) of the methodology described in the manuscript “Scan-to-decision workflow for clearance verification in light-rail depots: deriving obstacle-installation gauges from track tolerances”. The software is not the internal production code used in the case study; it is a clean re-implementation intended to enable independent reproduction. Implemented components: scenario-based reserve computation (S1–S8) for GLI/GNI; height-dependent envelope expansion from tabulated CIN/GLI/GNI perimeter points; 2D section-based geometric checking using signed distance / polygon intrusion; generation of CSV outputs and plots (including overlays). The repository includes unit tests and notebooks illustrating how to reproduce the example outputs using ESM1.